Etching Microstructures With Lasers

Consumer interest in analytics applications has prompted scientists in Germany to investigate how to use lasers to etch microstructures into thin glass. Through research, they found that irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a thousand times more sensitive to subsequent wet chemical etching.

Structuring process for glass using direct laser ablation with ultrafast laser pulses. Courtesy of Fraunhofer ILT, Aachen / Volker Lannert.
What this means to the scientific community is that it is possible to guide a laser beam — focused to within a diameter to a few µm — through a glass block and etch a fine tube through the volume of the glass. Applications include creating tiny holes, etching complete microfluidic systems into glass and making cuts with extreme high surface quality.

The BMBF-funded Femto Digital Photonic Production joint research project began in 2014. Representatives from the Fraunhofer Institute for Laser Technology (ILT) have been working alongside six companies — Amphos, Edgewave, TRUMPF, 4Jet, LightFab and Pulsar Photonics — to study new phenomena that arise when processing transparent materials with ultrafast laser pulses.

The researchers call the new procedure “selective laser etching” (SLE), which has been tested on several different types of glass materials, including quartz glass, sapphire, BOROFLOAT 33 and Corning Willow. Etch selectivities of 1000:1 between laser-structured and unstructured areas were reached in BOROFLOAT 33, and roughly 100:1 in Willow glass.

With the SLE technique, holes with particularly smooth edges can be bored through thin glass. Courtesy of Fraunhofer ILT, Aachen.
The next phase of the project delves into the actual understanding of the process and lasts until 2019. The researchers’ goal is to develop multiple beam systems for large surface use, as well as smaller systems for micro-processing, with other potential applications in biomedicine and electronics.

A noncrystalline, inorganic mixture of various metallic oxides fused by heating with glassifiers such as silica, or boric or phosphoric oxides. Common window or bottle glass is a mixture of soda, lime and sand, melted and cast, rolled or blown to shape. Most glasses are transparent in the visible spectrum and up to about 2.5 µm in the infrared, but some are opaque such as natural obsidian; these are, nevertheless, useful as mirror blanks. Traces of some elements such as cobalt, copper and...